1. Field of the Invention
The present invention relates to an optical waveguide for a touch panel.
2. Description of the Related Art
Touch panels are input devices for operating an apparatus by directly touching a display screen of a liquid crystal display device or the like by a finger, a special stylus or the like, and include a display which displays operation items, and detection means which detects the position (coordinates) of a portion of the display screen of the display touched by the finger or the like. Information of the touch position detected by the detection means is sent in the form of a signal to the apparatus, which in turn performs an operation specified by the touch position. Examples of the apparatus employing such a touch panel include ATMs in banking facilities, ticket venders in stations and portable game machines.
A detection device employing an optical waveguide is proposed as the detection means for detecting the finger touch position on the touch panel (see, for example, US 2004/0201579A1). As shown in FIG. 8, the optical waveguide is fitted around a periphery of a display screen of a rectangular display, and includes an L-shaped optical waveguide B1 and two linear optical waveguides B2, B3 respectively opposed to linear portions of the L-shaped optical waveguide B1. A multiplicity of light emitting cores which respectively emit light beams L parallel to the display screen of the display 11 are disposed in the liner portions of the L-shaped optical waveguide B1. A multiplicity of light receiving cores which respectively receive the light beams L emitted from the light emitting cores are disposed in the linear optical waveguides B2, B3 respectively opposed to the linear portions of the L-shaped optical waveguide B1. Thus, these three optical waveguides B1, B2, B3 cause the light beams L to travel in a lattice form on the display screen of the display 11. When a portion of the display screen of the display 11 is touched by the finger in this state, the finger blocks some of the light beams L. Therefore, the position of the portion touched by the finger is detected by detecting a light blocked portion by the optical waveguides B2, B3.
In the touch panel of the above-mentioned Patent Document, however, the L-shaped optical waveguide B1 which emits the light beams L and the two linear optical waveguides B2, B3 which receive the light beams are separately provided. Therefore, unless the two linear optical waveguides B2, B3 are accurately positioned with respect to the L-shaped optical waveguide B1, the optical waveguides B2, B3 cannot receive the light beams L, and the touch panel fails to function as the detection means. In addition, end faces of the respective cores serving as light outlet and inlet ports each have a very small size, so that the positioning is time-consuming.
In view of the foregoing, it is an object of the present invention to provide an optical waveguide for a touch panel which obviates the need for positioning the light receiving optical waveguides.